Esca of grapevine and training system

Abstract

Esca is currently, in France or even in Europe, the most concern grapevine disease. This trunk decline disease affects the longevity of vineyards. It is caused by the development of large inner necrosis in the grapevine wood associated with a wide fungal procession whose key players have already been identified. However the predisposing factors that favour the development of inner necrosis are still unknown or underestimated. According to the results of the various national observatories, the overall average impact by trunk diseases is now estimated at about 13% of vines impaired in their production potential. Esca of grapevine strongly contributes to this overall impact. But examination of plot by plot data showed a very high variability of damage and suggested the influence of cultural factors. A survey was undertaken from 2007 by UMR SAVE Bordeaux to try to identify relevant cultural factors that may influence the development of the disease. The study was first based on observations in Aquitaine in late summer. This study is presently integrated in a national project entitled “Assessment of the impact of cultural practices or environmental factors for the control of grapevine trunk diseases”. This project is financed via CasDAR (Account of Specific Affectation for Agricultural and Rural Development) and CNIV (National Committee of the Inter-occupations of Wines with Label of origin and with Geographical Indication). Comparable plot situations forming pairs with the same variety, the same age and very similar soil and climatic environments, but varying according to one several cultural factors, were determined. The ratings were applied to all symptoms on leaves and wood. Several selected examples showed that training decisions leading to long arms were generally less affected than the forms with very short arms or absent. The quality of the pruning system may also play a major role. The study also exhibited that the foliar symptoms are relevant clues to reveal the presence of the disease but not reliable indicators of impact. Real prospects in terms of reduced damage seem possible only by reasoning training decisions.